Swift - UIView moves when changing tab controller tabs - ios

Question

Inside the viewDidAppear I have a function that contains this code, in order to make a UIView:
let contentView = UIView()
func addSleepingView() {
contentView.backgroundColor = .systemYellow.withAlphaComponent(0.25)
view.addSubview(contentView)
contentView.translatesAutoresizingMaskIntoConstraints = false
contentView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
contentView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
// Anchor your view right above the tabBar
contentView.bottomAnchor.constraint(equalTo: (tabBarController?.tabBar.topAnchor)!).isActive = true
contentView.heightAnchor.constraint(equalToConstant: 50).isActive = true
let label = UILabel()
label.text = "Test"
label.frame = CGRect(x: 0, y: 0, width: 25, height: 34.0)
label.lineBreakMode = .byWordWrapping
label.numberOfLines = 0
label.textAlignment = .center
label.translatesAutoresizingMaskIntoConstraints = false
contentView.addSubview(label)
label.centerXAnchor.constraint(equalTo: contentView.centerXAnchor).isActive = true
label.centerYAnchor.constraint(equalTo: contentView.centerYAnchor).isActive = true
let button = UIButton()
button.setImage(UIImage(systemName: "arrow.clockwise", withConfiguration: UIImage.SymbolConfiguration(scale: .large)), for: UIControl.State.normal)
button.tintColor = .systemGray
button.frame = CGRect(x: self.view.bounds.width-42, y: 8, width: 34, height: 34.0)
button.isUserInteractionEnabled = true
button.addTarget(self, action: #selector(wakeupFunction), for: .touchUpInside)
contentView.addSubview(button)
let button2 = UIButton()
button2.setImage(UIImage(systemName: "exclamationmark.triangle", withConfiguration: UIImage.SymbolConfiguration(scale: .large)), for: UIControl.State.normal)
button2.tintColor = .label
button2.frame = CGRect(x: 8, y: 8, width: 34, height: 34.0)
button2.isUserInteractionEnabled = false
contentView.addSubview(button2)
contentView.bringSubviewToFront(button)
}
This is what it looks like:
Now this is exactly how I want it. The problem comes when I change tab. For example go to the last tab, and back to the first tab again. Then it looks like this:
What am I doing wrong here?

Answer 1

You can just add your code of activating constraints inside the DispatchQueue.main block
Updated Line you can change and it will start working as you're expectation.
// Anchor your view right above the tabBar
DispatchQueue.main.async
{
self.contentView.bottomAnchor.constraint(equalTo: (self.tabBarController?.tabBar.topAnchor)!).isActive = true
self.contentView.heightAnchor.constraint(equalToConstant: 50).isActive = true
}